There exist many instances, where a liquid in a container is to be dispensed repeatedly in the same pre-measured portion. Such situations include the dispensing of a liquid detergent into a washing machine, the addition of a concentrated liquid chemical to a processing container, etc. Traditionally, there exist two different methods for dispensing exactly-repeated portions of a liquid for such purposes. The first method consists of pouring the liquid into a measurement container in a first step and of emptying the measurement container into the final container in a second step. The chief disadvantages of this method are that an additional tool, the measurement container, must be provided and that the fluid has to be poured twice, thus increasing the chances of spilling the fluid. The second method consists in controlling the outlet of the liquid container by a tap and measuring the dispensed amount of liquid by reading the liquid level on a scale on the liquid container. Since the liquid container has to be held exactly vertically in order to correctly read the level of the liquid and since at least one hand is needed in order to control the tap, this method is mainly restricted to liquid containers installed at a fixed location and is not convenient for small transportable bottles. Additionally, at least a part of the container needs to be transparent in order to observe the level of liquid.
It would be of great advantage to have a liquid container for repeatedly dispensing a fixed volume of liquid in a single step without using an additional measurement container or a tap. Additionally, it would be very convenient if dispensing the defined amount of liquid were easy and no manual control of the apparatus would be necessary to establish the desired volume of liquid. It would be further advantageous if the operation of dispensing a constant volume of liquid could be repeated until the container is empty, without any need of additional operations to be carried out.